The polymeric lubricant having multi layer structure according to the present invention does not affect inherent physical properties of a vinyl chloride resin, and also minimizes an adhesive property to a surface of a processing machine upon its processing. It is provided in the form of powder and included in the polyvinyl chloride resin. Also, the polymeric lubricant according to the present invention has powder properties such as easy mass-production since it has an excellent fluidity at high temperature. Also, the polymeric lubricant having multi layer structure according to the present invention has an excellent ability to prevent its adhesion to a metal surface upon its processing so as to give a long-term workability to an extrusion, a calendering, a blow molding, an injection molding, etc. if an small amount of the powder of the present invention is mixed with a polyvinyl chloride resin.
Polyvinyl chloride resin has been widely used in various fields since it provides molded articles having excellent physical and chemical properties. However, polyvinyl chloride resin has various processing problems, including a narrow moldable temperature range, a high melting temperature and a low melt flow since its processing temperature is close to the thermal decomposition temperature. In addition, deposits are often formed, and therefore qualities of the final products are deteriorated since it tends to adhere to a metal surface of a processing machine when it is processed at high temperature.
Various techniques have been known to solve the above mentioned problems, especially the adhesive property to a metal surface of a processing machine. A representative technique is, for example to use a copolymerized polymeric lubricant including an alkyl(meth)acrylate monomer and an aromatic vinyl monomer as a major component in a vinyl chloride resin. U.S. Pat. No. 4,086,296 proposes a polymer made of a compositions of a low molecular weight polymer latex and a high molecular weight polymer, wherein the low molecular-weight polymer latex is obtained by polymerizing alkylacrylate, other acrylic monomer, and their copolymerizable vinyl-based monomer mixture at one step or multiple steps, and then the high molecular-weight polymer is obtained by further polymerizing methyl methacrylate, acrylate, other acrylic monomer, styrene, and their copolymerizable vinyl-based monomer mixture at one step or multiple steps. The acrylic composition polymer prepared thus has a rather excellent, but unsatisfactory, ability to prevent its adhesion to a metal surface, and also has a disadvantage in its mass-production because its powder fluidity is deteriorated at the high temperature in dry process.
U.S. Pat. No. 5,371,149 discloses a lubricant for a thermoplastic resin, which is a three-stage polymer, wherein methylmethacrylate is introduced as a major monomer in step 1 and step 3, and a copolymer consisting of alkylacrylate and an aromatic vinyl monomer is introduced as a major monomer in middle step (step 2), but the polymer does not meet a powder flowability at the high temperature in dry process, together with prevention of its adhesive property to a metal surface.
U.S. Pat. No. 5,942,581 proposes a method for using an alkylmethacrylate polymer having an alkyl group having 6 to 24 of carbon atoms, but the method has a disadvantage that it is also difficult to prevent its adhesive property and provide powder fluidity at high temperature.
E.U. Patent Application No. 1 209 203 A1 discloses a processing aid for thermoplastic resin, wherein its long-term duration of activity such as an adhesive property to a metal surface may be improved by using an organic peroxide including t-butylperoxy group as a polymerization initiator to copolymerize (meth)acrylate including an oxygen atom in addition to an ester bond with alkylacrylate, and their other copolymerizable vinyl monomer mixture. However, the processing aid prepared thus has an insufficient powder flowability at the high temperature.